After several months of using conversion tracking, I'm finally looking at the results. One thing I'm finding is that content matching just doesn't delivery the quality of traffic that search matching does. Conversion ratios from search matching for me has been several times as high as the conversion ratios from content matching. I can't justify the same CPC rates for content as I do for search. As a result, I've disabled content matching.
If Google ever adds the ability to do different bids for content matching (or Campaigns that just do content matching), I'll pick it back up. I could justify some of the content matching traffic, but the rates would have to be different.